Astronomers report on the search for extraterrestrial intelligence (SETI). They also describe how this search has changed over the past 40 years and how it has recently accelerated thanks to new search tools.

This NOVA scienceNOW segment:

reports that astronomers have been searching for extraterrestrial intelligence in the Milky Way galaxy for about 40 years.

acknowledges that only a small fraction of the cosmos has been searched and, to date, no extraterrestrial life has been found.

relates searching for alien signals to looking for a clear signal on the radio dial. In space, objects such as galaxies, pulsars, and quasars emit radiation across the full electromagnetic spectrum. Against this static-like "background noise," a narrowly focused signal in one band of the electromagnetic spectrum would likely signal the presence of an alien civilization.

theorizes that any technically advanced civilization would send electromagnetic signals into space, either deliberately or unintentionally. For example, electromagnetic waves from Earth-based television and radio broadcasts have been leaking into space for over 80 years and will have reached any planet within 80 light-years of Earth.

mentions that in the 1990s, NASA funded an extraterrestrial search facility based at the Arecibo radio telescope in Puerto Rico. This SETI funding was eliminated in 1993.

reports that there is a SETI renaissance thanks to a large grant from Paul Allen, a founder of Microsoft. New SETI components include the Allen Telescope Array, one of the largest, most sensitive radio telescopes in the world.

states that the scope of the search for extraterrestrial life is nearly impossible to comprehend. Our galaxy alone has about 300 million stars, and beyond it lie over 100 billion more galaxies.

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